1. Field of the Invention
The present invention relates to a detection system for obstruction particularly rearward of an automobile by means of a modulation light.
2. Description of the Prior Art
For detection of a rearward obstruction in an automobile or the like, a detection system shown, for example, in FIG. 1 is known well. The system comprises embedding a conductor 3 as a sensor in a rear bumper 2 of an automobile 1, detecting a change in electrostatic capacity (C) generated between the conductor 3 and an obstruction 4 in the form of a change in voltage value, thus detecting a presence of the obstruction 4 from the detected value. FIG. 2 is an equivalent circuit diagram thereof, wherein a voltage (V) coming out on an output terminal 6 from a power source 5 through a resistance (R) is changed according to the aforementioned electrostatic capacity (C), and thus a presence of the obstruction 4 can be known by detecting the voltage (V).
However, in the above-described detection system, since the electrostatic capacity (C) between the conductor 3 or a sensor and the obstruction 4 reacting thereto is simply detected, there may be a case where presence and position of the obstruction cannot securely be detected, and further the conductor is made to work as a sensor, it is easy to receive an influence of electromagnetic noise.